Masking material for applications in plasma etching

#1. Field of the Invention

#The present invention relates to masking materials for use in plasma etching, and more particularly to masking materials for applications in plasma etching of silicon and silicon-containing materials using chlorine and fluorine -based plasmas.

#2. Description of Related Art

#FIGS. 1, 2, 3 and 4 are cross-sections showing in progression a deep trench etch process in accordance with the present invention.

#Materials of the lead perovskite family PbZr.sub.x Ti.sub.1-x O.sub.3, in which the value of X varies from zero to one, have been discovered to be excellent masking materials in the etching of silicon and silicon-containing materials with chlorine and fluorine-based plasmas. Generally, materials of the lead perovskite family are suitable masking materials for any material that is etched in chlorine and fluorine -based plasmas such as, for example, plasmas derived from such gases as CCl.sub.4, CF.sub.4, SF.sub.6, CHF.sub.3, C.sub.2 F.sub.6, and Cl.sub.2. It is believed that the lead constitutient of the lead perovskite material contributes significantly to the etch-resistive properties. The lead perovskite material may include dopants (concentration less than about five 0 atomic percent) or modifiers (concentration greater than about five atomic percent). The most common dopants or modifiers for materials of the lead perovskite family are bismuth (Bi), iron (Fe), niobium (Nb), tin (Sn), and lanthanum (La), although other materials may also be used. See, e.g., Burfoot and Taylor, Polar Dielectrics and Their Applications, University of California Press, 1979, pp. 23-34.

#The etch-resistant properties of materials of the lead perovskite family were observed in various plasmas over the course of several experiments in which the value X, the plasma pressure, and the plasma temperature were varied. Some experiments were performed using a model Lam 490 plasma reactor, manufactured by and available from Lam Research. The electrode spacing and diameter were constant for the experiments, with the spacing being 1.0 centimeters and the diameter being 150 millimeters. The power applied was 220 watts for two minutes. The substrate temperature was maintained at 27.degree. C. The etch gas was a mixture of CCl.sub.4 and He, introduced at a flow rate of 80 SCCM and 40 SCCM respectively. The inlet pressure was maintained at 150 millitorr. The value of X in these experiments was 0.4 and 0.5. The samples were monitored for their chemical etch and sputter etch performance. No chemical etch was observed, and low sputter etch was observed.

#Other samples were etched using argon in a Perkin-Elmer 4400 series sputter etcher for ten minutes, at one thousand volts and ten milliTorr. The samples were monitored for their sputter etch performance. Low sputter etch was observed.